The Department of Defense is considering a transition to electric vehicles, in order to increase fuel efficiency and reduce the logistic tail. As these electric vehicles are deployed, many of them will need to be towed. The towing process provides a unique opportunity to use the electric motors in the vehicle to automatically charge the vehicle in tow.
Many electric and hybrid vehicles currently use technology called regenerative braking. In this method, the electric motor is used as a generator when decelerating, transforming the kinetic energy of the vehicle into electricity that is used for charging the batteries when braking or slowing down. One of the problems with regenerative braking is that the batteries usually have a charge rate that is significantly lower than the discharge rate. However, most vehicles can decelerate faster than they can accelerate.
Therefore, there is usually a significant amount of energy lost in the regenerative process, as the batteries cannot consume the amount of energy provided by the motor/generator when aggressive braking is needed. This excess energy is therefore usually dissipated as heat like in traditional disc or drum brakes commonly used by the automotive industry.
Regenerative braking technology can be performed by the primary electric motors of the electric vehicle, or by a secondary motor connected to the drive train similar to an alternator. If the regenerative braking is performed by the main electric motors of the electric vehicle, the amount of current generated can be significant, and possibly even exceed the charging rate of the batteries.